Conformational landscapes of bimesogenic compounds and their implications for the formation of modulated nematic phases

The twist-bend phase (NTB) is most commonly observed in materials with a gross-bent shape: dimers; bent-cores; bent-oligomers. We had suggested previously that the bend-angle of such systems effectively dictates the relative thermal stability of the NTB phase. However, our earlier paper relied on the use of a single energy-minimum conformer and so failed to capture any information about flexibility and conformational distribution. In the present work, we revisit our hypothesis and examine a second set of dimers with varying linking groups and spacer composition. We have improved on our earlier work by studying the conformational landscape of each material, allowing average bend-angles to be determined as well as the conformer distribution. We observe that the stability of the NTB phase exhibits a strong dependence not only on the Boltzmann-weighted average bend-angle (rather than just a static conformer), but also on the distribution of conformers. To a lesser extent, the flexibility of the spacer appears important. Ultimately, this work satisfies both theoretical treatments and our initial experimental study and demonstrates the importance of molecular bend to the NTB phase

The Dependency of Nematic and Twist-bend Mesophase Formation on Bend Angle

We have prepared and studied a family of cyanobiphenyl dimers with varying linking groups with a view to exploring how molecular structure dictates the stability of the nematic and twist-bend nematic mesophases. Using molecular modelling and 1D (1)H NOESY NMR spectroscopy, we determine the angle between the two aromatic core units for each dimer and find a strong dependency of the stability of both the nematic and twist-bend mesophases upon this angle, thereby satisfying earlier theoretical models

Combined Microscopy, Calorimetry and X-ray Scattering Study of Fluorinated Dimesogens

The material FDO11DFCB3 (compound 2 in this work) remains the only example of a liquid-crystalline material to exhibit a phase transition from the heliconical twist-bend phase into a lamellar smectic A mesophase, additionally this material exhibits a previously unidentified mesophase. We have prepared and characterised several homologues of this compound, with each material subjected to an in-depth analysis by optical microscopy, calorimetry and small angle X-ray scattering studies. Despite FDO11DFCB3 being similar in chemical structure to the novel materials presented herein its liquid-crystalline behaviour is rather different, indicating an unexpected sensitivity of the twist-bend phase to molecular structure

Understanding the twist-bend nematic phase: the characterisation of 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OCB) and comparison with CB7CB

Acknowledgements The FFTEM data were obtained at the (Cryo) TEM facility at the Liquid Crystal Institute, Kent State University, supported by the Ohio Research Scholars Program Research Cluster on Surfaces in Advanced Materials. ODL acknowledges the support of NSF DMR-1410378 grant. The authors are grateful for financial support from MINECO/FEDER MAT2015-66208-C3-2-P and from the Gobierno Vasco (GI/IT-449-10) OA via RSC Gold4GoldPeer reviewedPublisher PD

Signal transduction in a covalent post-assembly modification cascade

Natural reaction cascades control the movement of biomolecules between cellular compartments. Inspired by these systems, we report a synthetic reaction cascade employing post-assembly modification reactions to direct the partitioning of supramolecular complexes between phases. The system is composed of a self-assembled tetrazine-edged FeII8L12 cube and a maleimide-functionalized FeII4L6 tetrahedron. Norbornadiene (NBD) functions as the stimulus that triggers the cascade, beginning with the inverse-electron-demand Diels–Alder reaction of NBD with the tetrazine moieties of the cube. This reaction generates cyclopentadiene as a transient by-product, acting as a relay signal that subsequently undergoes a Diels–Alder reaction with the maleimide-functionalized tetrahedron. Cyclooctyne can selectively inhibit the cascade by outcompeting NBD as the initial trigger. Initiating the cascade with 2-octadecyl NBD leads to selective alkylation of the tetrahedron upon cascade completion. The increased lipophilicity of the C18-tagged tetrahedron drives this complex into a non-polar phase, allowing its isolation from the initially inseparable mixture of complexes

What is dignity? A literature review and conceptual mapping

Background Whilst dignity is a prominent issue in health care, no standardised questionnaire exist that capture the multi-faceted nature of it. Those questions that do exist cannot be used in cost-effectiveness analysis as they lack the relevant measurement properties required. This study describes the work done to date on a programme of research undertaken in collaboration between the University of Sheffield and the Devices for Dignity (D4D) Project that assesses what is meant by dignity and to what extent it relates to more readily recognised concepts used within health services research. Methods A literature review was undertaken based on documents known to the authors and the Devices for Dignity (D4D) project based in Sheffield, together with references ‘pearl grown’ from the documents plus ad hoc electronic searches. A qualitative framework was used to identify those concepts that were used in the literature and an attempt made to show how each of these were related in a ‘conceptual map’. A possible set of questions was then developed that linked to the conceptual map. Results Only a few journal articles were found that explored the concept of dignity in theoretical terms. Most articles took a nursing perspective and so were largely focused on carer-patient interactions, although other aspects of the care process were also included, such as the care environment. Others took a broader perspective and looked at dignity as a concept across all aspects of life. A wide range of pre-existing questions were identified from the literature that attempted to measure dignity directly, or indirectly through factors that are thought to influence it. Other concepts and questions related to dignity were identified that encompassed notions of patient satisfaction, patient experience, autonomy, control, self-esteem and quality of life. We developed our own conceptualisation of dignity that attempts to describe the links between dignity, the environment, processes of care, capabilities, functionings and well-being. This framework is thought to work quite well in describing the various influences on dignity, capturing all the identified concepts and linking into an overall model of well-being that has been developed by Sen in the broader economics literature. Conclusions Many different definitions and conceptualisations of dignity exist in the literature. Consequently it is unclear what it means, how it should be measured and how it relates to other concepts used in health technology assessment. We have developed a conceptual map of dignity and well-being that is capable of incorporating the vast majority of the care-related issues highlighted in the literature. This appears to be a valuable starting point for further research to measure dignity, and apply it in health technology assessment alongside generic instruments such as the EQ-5D

Palladium-Based Metal–Ligand Assemblies: The Contrasting Behavior upon Addition of Pyridine or Acid

The stability of five different [Pd<i>_n</i>(N-donor)<i>_m</i>]^2<i>n</i>+ assemblies was examined by performing disassembly experiments with pyridine and with trifluoroacetic acid. Pyridine-induced disassembly was found to be most pronounced for Pd complexes containing N-donor ligands of low basicity. At the same time, these assemblies displayed high acid resistance. The contrasting stability in the presence of acid or pyridine can be used for the pH-controlled switching between different metallosupramolecular structures